Cable gripping devices are in wide use and comprise a self-adjusting cable gripping unit which automatically adapts itself to gripping a stranded cable. In seal use, a cable is formed with a swaged flag at one end to form an integral head member for the cable end. The other end of the cable is free. The cable free end is slipped or otherwise passed through an opening of a structure to be locked, for example, two hasps of a lock arrangement or other arrangement in doors, walls and the like for securing two elements together.
After the cable is slipped through the hasps or other lock arrangement, the cable gripping unit receives the free end of the cable and the cable is slid through the unit which has a bore therein including a cable gripping structure within the bore which slides over the cable as the unit is slid along the cable. When the unit reaches a desirable position adjacent to the hasp or other structure to which the cable is to be locked the unit is left in place at that location. Any attempt to remove the unit by sliding the unit in a reverse direction along the cable is precluded by a gripping structure within the unit bore. If the gripping structure is attempted to be slid in the reverse direction, it wedges against the cable and locks thereto. The gripping unit housing and the flag at opposing ends of the cable lock the cable and the hasp together.
In U.S. Pat. No. 3,852,850, a cable gripping unit is disclosed. This unit includes a helical spring, a cable receiving cup and a gripping member comprising a jaw retaining member and jaw segments. A shell formed of metal has a bore terminating in a cable accommodating opening and a cylindrical portion terminating in a reduced diameter opening proving an inwardly projecting annular shoulder. The gripping member and jaw segments are received in the bore. The gripping member is urged toward a reduced end of the opening of the gripping unit shell. The jaw retaining member is formed of an elastic material with the jaw segments held in slots in the retaining member. A spring urges the jaw segments in wedging engagement in the shell bore. This structure requires a number of different elements including separate jaw segments and a jaw retaining member.
U.S. Pat. No. 3,868,748 ('748) discloses a tendon gripping and release assembly somewhat similar to that disclosed in U.S. Pat. No. 3,852,850. In the '748 patent, a tapering casing housing includes spring compressed wedge segments arranged to form a bore therebetween for reception and retention of a steel tendon inserted in the casing. The wedged segments are urged towards the small end of the tapering casing by a spring. An elongated release member extends transversely through the small end of the tapered casing and engages one end of the wedge segments. The release member urges the wedged segments rearwardly against the tension of a spring to release the grip on the tendon and permit removal thereof from the assembly.
In those instances where it is not desirable to release the tendon, the use of a release mechanism as disclosed in this patent is not desirable. For example, where it is desired to permanently lock to the tendon, a release mechanism is not needed.
In U.S. Pat. No. 3,994,521, a portable cable lock is employed with a ball detent mechanism. The balls provide similar action as that of the wedge segments in the patents discussed above. In this arrangement, a locking shell is formed with a central passageway which is internally tapered with an opening that changes from conical to triangular and which carries spring loaded ball bearings and a retainer such that a cable can be inserted through the central opening in a first direction. This depresses the spring and allows the balls to relieve pressure on the cable in the first direction but which provide substantial locking pressure on the cable when the cable is placed under tension in the opposite direction.
A still further arrangement is disclosed in U.S. Pat. No. 1,577,678 which discloses a fastening means employing a similar type of cable gripping structure. U.S. Pat. No. 899,776 discloses a trolley wire splicer employing a number of jaws. This arrangement is somewhat similar to that disclosed in the U.S. Pat. No. 3,852,850 discussed above.
A common problem with the above recognized by the present inventors is the possibility of the cable twisting relative to the gripping or locking devices within the locking assembly housing. When a stranded cable twists relative to the gripping members inside the housing, the helix of the strands acts as a thread such that the cable may be twisted out of engagement with the gripping or locking devices. This is a problem with seals as disclosed, for example in the '521 patent above, because the cables are short and can be manually twisted.
This is not a problem with many of the prior art because the cables are not twistable relative to the locking assembly. For example, in U.S. Pat. No. 2,988,727 the cables are used in transmission work, mechanical apparatus and structural work. As a further example, in U.S. Pat. No. 3,374,511 to Barker the cables are used in pre-stressed concrete structures. Cables in guy wires, concrete, transmission lines and other typical structural uses are not normally twisted in use.
In commonly owned U.S. Pat. No. 5,222,776 a security seal is disclosed which uses balls for wedging and locking a cable. Here the problem of twisting is recognized in this type of seal and is dealt with in the disclosed arrangement. However, it is not generally known in jaw type locking devices such as in Barker, that cable twisting is a problem because the locking jaws are different than the ball structure and the cables normally used therewith in the prior art do not twist.
The prior art discussed above utilize a spring for urging the gripping member in engagement with the cable or tendon. This is costly as the housing or casing needs to be elongated to accommodate the spring and these represent additional cost.
The present inventors recognize a need for a low cost simplified cable locking seal for securing a cable thereto which is not subject to the twisting release action of stranded cables. The present inventors also recognize a need for a low cost seal that does not utilize a spring to be operative.